Semiconductor buried layers are widely used in integrated circuit (IC) devices and manufacturing processes. Particularly, semiconductor buried layers are widely used in semiconductor devices including transistors, diodes, and metal-oxide-semiconductor (MOS) transistors in IC processes that require high performance. Development of the buried layer technology greatly affects IC performance and IC manufacturing process development.
Buried layer technology may reduce on-resistance of the IC devices and may improve degree of integration and anti-interference capability, thereby reducing power consumption and parasitic capacitance to increase efficiency of the IC devices. Specifically, for a bipolar junction transistor (i.e., BJT or bipolar transistor), presence of a buried layer can reduce resistance of the collector and improve characteristic frequency. Further, presence of a heavily doped N-type buried layer can effectively prevent the thin epitaxial layer, the lightly-doped collector region epitaxial layer, from being fully converted to a space potential barrier region by a reverse bias voltage, thereby effectively improving the voltage tolerance of the bipolar transistor device.
A conventional buried layer process may include the following steps: (1) providing a substrate and forming an oxide layer on the substrate, the oxide layer reducing occurrence of ion tunneling effect during ion implantation and protecting lattice arrangement of the substrate surface; (2) using a photoresist pattern to form an opening for doping a buried layer; (3) forming the buried layer by doping atoms in the substrate, based on the photoresist pattern; and (4) removing the photoresist pattern and the oxide layer and then forming an epitaxial layer over the entire substrate surface.
As such, conventional methods for forming a buried layer need to form an epitaxial layer on the substrate after forming the buried layer. However, due to high manufacturing cost of the epitaxial process, manufacturing cost of the IC devices is increased.